R. E. Ekstrom U.S. Pat. No. 4,121,460 describes an instrument designed to measure the temperature of a device such as a thermometer bulb, a Calrod heating element, etc. The instrument includes a housing adapted to enclose the device and temperature responsive parts within the housing that engage the device and sense its temperature.
In addition to the above Ekstrom patent, Howell U.S. Pat. No. 2,854,844 discloses a portable test unit for a thermometer bulb wherein the bulb is placed in a heated enclosure. The enclosure is heated by a resistance wire heater and a variable power source. A metal heat conductive sleeve encloses the bulb, and in one arrangement shown in the patent, a thermocouple engages the sleeve. The patent also makes a reference to obtaining an accurate average temperature reading. Evans' U.S. Pat. No. 2,658,380 also shows a portable test unit including a built-in heater.
The following U.S. patents were cited as references in the Ekstrom U.S. Pat. No. 4,121,460 and may be considered pertinent: U.S. Pat. Nos. 1,762,859, 2,694,313, 3,134,008, 3,155,237, 3,757,207 and 3,797,310.
A goal not adequately reached by the instruments described in the foregoing patents is that of a portable instrument capable of quickly and accurately measuring the temperature of an elongated object and adaptable to use with objects of a variety of sizes and designs.
It is accordingly a general object of the present invention to provide a novel and improved test instrument that serves the foregoing needs.